1) Plants are multicellular, eukaryotic organisms that contain cellulose in their cell walls and produce their own food through photosynthesis using chlorophyll. 2) There are four major groups of plants - bryophytes, seedless vascular plants, gymnosperms, and angiosperms - which are separated based on their vascular tissue, seeds, and flowers. 3) Angiosperms are the most common and successful group, as their flowers attract animals to help with pollination and their seeds develop protected inside the flower.